Mechanical hammer



Limb-M March 14, 1961 F/G. Z.

J. MORRIS 2,974,535

MECHANICAL HAMMER Filed Sept. 8, 1958 /A/ VE N 70/? JOSEPH Mom? /5 BY HIS ATTORNEYS HARE/.5, MECH, P037252 8: HARE/6 United States Patent MECHANICAL HAMMER Joseph Morris, 111 Marquey Place, Pacific Palisades, Calif.

Filed Sept. 8, 1958, Ser. No. 759,716

11 Claims. (Cl. 74-22) The present invention relates to a rotary mechanical hammer which is an improvement on that of my copending patent application Serial No. 529,815, filed August 22, 1955, now Patent No. 2,889,711, granted June 9, '1959, and which is also an improvement on that of my co-pending patent application Serial No. 569,440, filed March 5, 1956, now Patent No. 2,869,374, issued January 20, 1959.

The mechanical hammer of the invention simultaneously reciprocates and continuously rotates a tool connected thereto, which tool may be a drill, a riveting head, an impact wrench, or the like. Also, the mechanical hammer may be utilized to operate any device requiring vibratory power, such as a vibrating pump, for example. While not limited thereto, the present invention is of particular utility in the drilling of such materials as rock, concrete, brick, or the like, the hammering action applied to a drill by the mechanical hammer of the invention, coupled with the continuous rotary motion imparted to the drill thereby, resulting in extremely high drilling rates in materials of this character.

Considering the present invention more specifically now, it contemplates a mechanical hammer which includes a housing having therein stationary and movable cam members, the movable cam member being rotatable about and reciprocable along the axis of the cam members. Interengageable, circumferentially spaced cam elements projecting from cam surfaces on the cam members produce reciprocatory movement of the movable cam member in response to rotation thereof, rotation of the movable cam member being produced by a drive means slidably connected to one end of a shaft on which the movable cam member is mounted. The desired tool or device is connected to the other end of such shaft so that the rotational movement of the shaft produced by the drive means, and the reciprocatory movement of the shaft resulting from the interengagement of the interengageable cam elements on the two cam members, are transmitted to the tool. With this construction, the movable cam member and the shaft on which it is mounted are axially displaced periodically in a manner to produce sharp, hammering blows at the tool or device connected to such shaft.

The cam elements projecting from the cam surfaces on the two cam members preferably are rotatable cam elements, such as balls, rollers, or the like, disposed in cavities in the cam surfaces. Preferably, the cavities in which the rotatable cam elements are disposed have substantially flat bottom walls and have side walls substantially perpendicular to such bottom walls. In other words, the cavities and cam elements, when viewed in cross section, are square and circular, respectively. With this construction, there is substantially no tendency for the cam elements to climb out of the cavities as they rotate therein, the cam elements being unable to obtain sufficient purchase on the perpendicular side walls of ble extent. Consequently, the reciprocatory impulses imparted to the movable cam member are perfectly constant in amplitude or magnitude since the cam elements do not tend to climb out of the cavities as they rotate therein.

One object of the invention is to provide the cam members with projections extending inwardly of the cavities at the open ends thereof to retain the rotatable cam elements in the cavities. These cam-element-retaining projections may be inwardly extending lugs, inwardly extending flanges, or the like.

An important object of the invention is to provide a construction of the foregoing nature wherein the distances between the bottom walls of the cavities and the inwardly extending projections are greater thanthe corresponding dimensions of the cam elements and wherein the transverse dimensions of the cavities are greater than the corresponding dimensions of the cam elements so that the cam elements are loosely disposed in the cavities, both transversely of the cavities and longitudinally or axially thereof. This construction is important since it insures that the cam elements rotate freely in their cavities, while still being restrained against movement out of the cavities by the inwardly extending projections mentioned.

Another important object of the invention is to provide a housing for the mechanical hammer which includes a compartment open at one end of the housing and having longitudinal spline ways extending in a direction from the open end of the housing toward the other end thereof and terminating in shoulders disposed in a common plane perpendicular to the axis of the ham mer, the stationary cam member having splines thereon which are disposed in the spline ways and which are clamped against the shoulders mentioned to secure the stationary cam member to the housing in a positive and rigid manner while permitting easy installation and removal of the stationary cam member.

Another object is to provide a construction wherein the splines on the stationary cam member are held against the shoulders at the ends of the spline ways by a spacer clamped between the stationary cam member and a head threaded into and closing the open end of the compartment in the housing.

Another object is to provide a mechanical hammer wherein the compartment within the housing is provided with an end wall adjacent the movable cam member which carries rotatable thrust bearing elements engageable by the movable cam member when the movable cam member is not biased toward the stationary cam member by a load applied to a tool connected to the movable cam member. This construction minimizes friction when the mechanical hammer of the invention is not operating under load, which is an important feature.

The drive means for rotating the movable cam member comprises a telescopic connection between a drive shaft and a shaft on which the movable cam member is mounted, and comprises a floating drive pin ertending through an opening in one of the shafts into longitudinal grooves in the other to transmit rotation of the drive shaft to the shaft carrying the movable cam member while permitting reciprocatory motion of the latter relative to the stationary cam member.

An important object of the invention is to provide a rectangular floating drive pin disposed in a rectangular opening, the width of the floating drive pin in the direction of reciprocation of the movable cam member approaching the length thereof in a direction perpendicular to the direction of reciprocation. This drive pin construction provides a rugged connection capable of withstanding large torques.

members each including two discs one of which has the cam-element cavities formed therein and the other of which is seated against the first and provides the bottom walls of such cavities. With this construction, the cam elements are easily assembled with the cam members, the cam elements being retained within their cavities by the inwardly extending projections at the open ends of the cavities once the discs forming each cam member have been secured together. 7

A further object is to provide cam members each having two radially spaced, circumferentially extending rows of rotatable cam elements, the cam elements of one such row on one cam member being circumferentially staggered relative to the cam elements of the other row thereon. This construction results in a large number of impacts per revolution.

The foregoing objects, advantages, features and results of the present invention, together with various other objects, advantages, features and results thereof which will be evident to those skilled in the art to which the invention pertains, may be achieved with the exemplary embodiment of the invention described in detail hereinafter and illustrated in the accompanying drawing, in which:

Fig. 1 is a longitudinal sectional view of an apparatus including a mechanical hammer which embodies the invention;

Figs. 2 and 3 are transverse sectional views respectively taken along the arrowed lines 22 and 3'3 of Fig. l; and

Fig. 4 is an enlarged, fragmentary longitudinal sectional view of a cam member of the mechanical hammer showing details of the structure thereof, Fig. 4 duplicating a portion of Fig. 1 on a larger scale.

In the drawing, the numeral 8 designates a mechanical hammer of the invention having a generally cylindrical housing .10 which is provided with circumferentially spaced, external longitudinal ribs 12 for heat dissipation purposes. The housing 18 is provided with an axial bore 14 therethrough and successively larger counterbores 16, 18 and 20, these counterbores providing within the housing a generally cylindrical chamber 22 having an open end 24 and a closed end 26. The open end 24 of the chamber 22 is closed by a head 28 which is threaded into the counterbore 20.

The hammer S is mounted on an electric motor 30, or other rotary prime mover, by threading an axial cylindrical extension 32 of a housing 34 of the motor into a counterbore 36 in the head 28. The motor 30 is provided with a shaft 38 which projects from the extension 32 and which is utilized to drive the hammer 8 in a manner to be described hereinafter.

The peripheral wall of the counterbore 18 in the housing is provided with short, circumferentially spaced, longitudinally extending spline ways 40 which extend from a shoulder 42 at the junction of the counterbores 18 and to a shoulder 44 at the junction of the counterbores 16 and 18. The bottom walls of the spline ways lie in a circle of the same diameter as the circle defined by the counterbore 20, and the spline ways terminate at their ends farthest from the open end 24 of the chamber 22 in shoulders 46 located in the same plane as the shoulder 44, which plane is perpendicular to the axis of the hammer 8. A stationary cam member 48 is disposed in the chamber 22 and is provided with splines 50 respectively disposed in the spline ways 40 and respectively seated on the shoulders 46, the stationary cam member also being seated on the annular shoulder 44. The stationary cam member 48 is clamped against the annular shoulder 44 and the splines 50 thereon are clamped against the shoulders 46 by a spacer 52 seated against the head 28. With this construction, the stationary cam member 48 is readily installed, it merely being necessary to insert it into the open end 24 of the chamber 22 in such a manner that the 4 splines 50 thereon enter the spline ways 40. The spacer 52 is then inserted into the open end 24 of the chamber 22 and the head 28 is threaded into the counterbore 20 far enough to engage the spacer and cause it to seat the stationary cam member 48 on the annular shoulder 44 and to seat the splines 50 on the shoulders 46. The stationary cam member 48 may obviously be removed by reversing the foregoing procedure. Thus, the present invention provides a very simple way of installing and removing the stationary cam member 48 and of locking it in place in the housing 10, which is an important feature.

Disposed between the stationary cam member 48 and the closed end 26 of the chamber 22 in face-to-face relation with the stationary cam member is a movable cam member 54 carried by a shaft 56 which is journalled in a bearing 58 disposed in the bore 14 on one side of the cam members 48 and 54 and a bearing 60 on the opposite side thereof. The bearing 60 is disposed in a counterbore 62 in an internal axial boss 64 on the head 28 and is disposed in a bore 66 in the stationary cam member 48.

The movable cam member 54 is rotatable and reciprocable in the bearings 58 and 60, the stationary and movable cam members 48 and 54 co-operating in a manner to be described to produce axial movement of the movable cam member away from the stationary cam member periodically in response to rotation of the movable cam member. Considering the manner in which the movable cam member is rotated, the shaft 56 is provided adjacent the motor 39 with a counterbore 68 into which extends a drive shaft 70, the latter projecting through a bore 71 in the head 28 and being suitably connected to and held against axial movement by the shaft 38 of the motor. For example, there may be a splined connection between the shafts 38 and 70. The drive shaft is provided within the counterbore 68 with a rectangular transverse opening 72 which receives a rectangular, floating drive pin 74 projecting transversely from the opening 72 into circumferentially spaced, longitudinal grooves 76 in the wall of the counterbore 68 in the shaft 56. With this construction, the shaft 56 and the movable cam member 54 thereon may reciprocate relative to the drive shaft 70 while the drive shaft transmits rotation thereto. The width of the drive pin 74 in the axial direction approaches its length in the transverse direction to provide a rugged connection capable of transmitting large torques, which is an important feature.

The chamber 22 is partially or completely filled with a lubricant which lubricates various parts within the chamber and which conducts heat to the housing 10 for dissipation by the ribs 12. In order to prevent leakage of such lubricant from the chamber 22, suitable lubricant seals 80 and 82 are provided. The seal 80 engages the drive shaft 70 and is disposed in a counterbore 84 in the head 28. The seal 82 engages the shaft 56 and is disposed in a counterbore 86 in a seal retainer 88 threaded into a counterbore 90 in the end of the housing 10 opposite the motor 30.

The shaft 56 is provided therein with an axial bore 92 communicating with radial ports 94 and 96, the ports 94 constantly communicating with the interior of the 'outwardly of the ports 96.

The shaft 56 projects from the housing 10 through a bore in the retainer 88 and is threaded at its outer end, as indicated at 102, to receive a chuck, or the like, for holding a drill, or other tool or device to be operated by. the mechanical hammer 8.

Considering the stationary cam member 48 now in more detail, it is provided with a transverse surface k 104 carrying radially spaced, circumferentially extending iunerand outer rows 106 and 108 of balls 110 respectively disposed in cavities 112 in such surface. Similarly, the movable cam member 54 is provided with a transverse surface 114 which is disposed in face-to-face relation with the transverse surface 104 and which carries radially spaced, circumferentially extending inner and outer rods 116 and 118 of balls 120 respectively disposed in cavities 122 in such surface. As the movable cam member 54 is rotated in the manner hereinbefore described, the balls 120 of the inner row 116 periodically engage the balls 110 of the inner row 106 and the balls 120 of the outer row 118 periodically engage the balls 110' of the outer row 108 to displace the movable cam member 54 axially away from the stationary cam member 48, the movable cam member being displaced toward the stationary cam member after each such displacement away from the stationary cam member by the load applied to the shaft 56 by the tool or device connected thereto. Between engagements of the balls 120 with the balls 110', the balls 120 engage the cam surface 104 and/or the balls 1'10 engage the cam surface 114, when the hammer 8 is under load.

It will be noted that the balls 110 of the inner and outer rows 106 and 108 on the stationary cam member 48 are circumferential'ly staggered, while the balls 120 of the inner and outer rows 116 and 118 of the movable cam member 54 are not. With this construction, the balls 120 of the outer row 118 engage the balls 110 of the outer row 108 between engagements of" the balls 120 of the inner row 116 with the balls 110 of the inner row 106. Thus, by utilizing two rows of balls on each of the cam members 48 and 54 and by staggering one of the rows of balls on one of the cam members relative to the other row of balls on such cam member, the number of imp-acts imparted to the tool or device connected to the shaft 56 per revolution of the shaft is doubled, which is an important feature.

As best shown in Fig. 4 of the drawing, the ball cavities 112 are substantially square in cross section, the ball cavities 112 having substantially fiat bottom walls 124 and side walls 126 perpendicular thereto. As previously pointed out, this squareness ofthe cavities 112 minimizes any tendency of the balls 110 to climb out of the cavities as the balls 110 rotate. The cavities 122 containing the balls 120 have similar configurations and the same considerations are applicable thereto.

Again as best shown in Fig. 4, the stationary cam member 48 provides adjacent the open ends of the cavities 112, i.e., adjacent the ends thereof nearest the movable cam member 54, inwardly extending projections 128 which retain the balls 110 within the cavities 112. Each projection 128 may comprise one or more inwardly extending lugs at the open end of the corresponding cavity, or, as shown, may comprise an annular flange. In either event, the balls 110 are positively retained within the cavities 112. The cavities 122 have the same structure to retain the balls 120 therein so that a further description is unnecessary.

The distances between the bottom walls 124 of the cavities 1'12 and the projections 128 are greater than the corresponding dimensions of the balls 110, and the transverse dimensions or diameters of the cavities 112 are greater than the corresponding dimensions of the balls 110 so that the balls 110 fit loosely in the cavities 112 between the bottom walls 124 and the projections 128 and between the side walls 126. This loose fit for the balls 110 in all direct-ions insures that they will rotate freely, which is an important feature. Similar considerations are applicable with respect to the balls 120 and the cavities 122, the balls 120 also having loose fits in the cavities 122 in all directions.

The stationary cam member 48, as best shown in Fig. 4 of the drawing, includes two discs 130 and 132 held together by circumferentially spaced screws 134 extending through the disc 130 and threaded into the disc 132. The cavities 112 are formed in the disc 132 and the bottom walls 124 of such cavities are formed by the disc 130, which is seated against the disc 132 and held in this position by the screws 134. With this construction, the annular projection 128 for retaining each ball may readily be formed by drilling the corresponding cavity 112 with a tapered drill, and terminating the drilling operation before going all the way through the disc 132, thereby leaving the annular projection 128. Also, the balls 110 may be installed in the cavities 112 very readily with this construction, by merely dropping them into the cavities from, in effect, the bottom ends of such cavities, the balls being retained by the projections 128. Thereafter, the disc 130 is placed against the disc 132 and secured by the screws 134 to close the bottom ends of the cavities 112.

Similarly, the movable cam member 54 comprises two discs 136 and 138, the disc 136 being integral with the shaft 56 and the disc 133 being threaded thereonto. The cavities 122 for the balls 120 are formed in the disc 138 in the same manner that the cavities 112 are formed in the disc 132. After the balls 120 are disposed in the cavities 122, this being done with the disc 138 inverted with respect to the position shown in Fig. l, the shaft 56 is threaded into the disc 138 to bring the disc 136 into engagement with the disc 138 so as to, in effect, close the bottoms of the cavities 122.

The closed end 26 of the chamber 22 comprises a plurality of radial webs 140 separated by wells 142 which contain portions of the lubricant within the chamber 22 to facilitate heat conduction to the exterior of the housing 10. The webs 140 are provided therein with cavities 144 for balls 146 which are rotatably held in such cavities by peening, staking, or the like. The balls 146 project from the cavities 144- toward and are engageable by the disc 136 of the movable cam member 54 when there is no load on the tool or device connected to the shaft 56 so that the balls 120 carried by the movable cam member are out of engagement with the balls 1-10 carried by the stationary cam member 48. Thus, when the hammer 8 is in the position shown, and no load is applied to the tool or device connected to the shaft 56, gravity tends to move the movable cam member 54 downwardly so that the lower surface of the disc 136 thereof rests on the balls 146. Consequently, the balls 146 act as thrust hearings to minimize friction while the hammer 8 is in operation under no load, which is an important feature.

Although an exemplary embodiment of the present invention has been disclosed herein for purposes of illustration, it will be understood that van'ous changes, modifications and substitutions may be incorporated in such embodiment without departing from the spirit of the invention as defined by the claims which follow.

I claim as my invention:

1. In a rotary hammer, the combination of: a housing providing an axis; a stationary cam member in and carried by said housing and having a cam surface which extends generally transversely of said axis, said cam surface of said stationary cam member being provided with circumferentially spaced cavities therein having substantially flat bottom walls and having side walls substantially perpendicular to said bottom walls thereof; a shaft in said housing and extending axially through said stationary cam member, said shaft being rotatable about and reciprocable along said axis; a movable cam member in said housing and fixed on said shaft, said movable cam member having a cam surface which extends generally transversely of said axis and which faces said cam surface of said stationary cam member, said cam surface of said movable cam member being provided with circumferentially spaced cavities therein having substantially flat'bottom walls and having side walls substantially perpendicuable cam members being provided with projections which extend inwardly of said cavities at the open ends thereof to retain said rotatable cam elements in said cavities, the distances between said bottom walls of said cavities and said inwardly extending projections being greaterthan the corresponding dimensions of said rotatable cam elements and the transverse dimensions of said cavities being greater than the corresponding dimensions of said rotatable cam elements so that said rotatable cam elements fit loosely in said cavities.

2. In a rotary hammer, the combination of: axially spaced, stationary and movable cam members respectively having transverse cam surfaces disposed in faceto-face relation, each of said cam surfaces being provided With circumferentially spaced cavities therein having substantially flat bottom walls and having side walls substantially perpendicular to said bottom walls thereof; and rotatable cam elements of circular cross section respectively disposed in and projecting from said cavities in each of said cam surfaces, said rotatable cam elements in said cavities in said cam surface of said movable cam member being engageable with said rotatable cam elements in said cavities in said cam surface of said stationary cam member so as to produce axial movement of said movable cam member in response to rotation thereof, said stationary and movable cam members being provided with projections which extend inwardly of said cavities at the open ends thereof to retain and rotatable cam elements in said cavities, the distances between said bottom walls of said cavities and said inwardly extending projections being greater than the corresponding dimensions of said rotatable cam elements and the transverse dimensions of said cavities being greater than the corresponding dimensions of said rotatable cam elements so that said rotatable cam elements fit loosely in said cavities.

3. A rotary hammer as defined in claim 2 wherein each of said cam members includes two discs, one having holes therethrough forming said cavities and the other being seated against the first and forming said bottom walls of said cavities.

4. In a rotary hammer, the combination of: a housing providing an axis and providing a generally cylindrical chamber which is open at one end of said housing, the peripheral wall of said chamber being provided with circumferentially spaced spline ways extending parallel to said axis in a direction from said one end of said housing toward the other end thereof and terminating in shoulders disposed in a plane perpendicular to said axis; a stationary cam member disposed in said chamber and having thereon circumferentially spaced splines respec tively disposed in said spline ways and seated against said shoulders; means connected to said one end of said housing for maintaining said splines seated against said shoulders; a movable cam member disposed in said chamber between said stationary cam member and said other end of said housing, said movable cam member being rotatable and axially reciprooable in said chamber; interengageable cam elements on said stationary and movable cam members for moving said movable cam member axially in response to rotation thereof; and means for rotating said movable cam member.

5. In a rotary hammer, the combination of: a housing providing an axis and providing a generally cylindrical chamber which is open at one end of said housing, the

peripheral wall of said chamber being provided with circumferentially spaced spline ways extending parallel to said axis in a direction from said one end of said housing toward the other end thereof and terminating in shoulders disposed in a plane perpendicular to said axis; a stationary cam member disposed in said chamber and having thereon circumferentially spaced splines respectively disposed in said spline ways and seated against said shoulders; means connected to said one end of said housing for maintaining said splines seated against said shoulders, including a head threaded into and closing said open 'end of said chamber and a spacer clamped between said head and said stationary cam member; a movable cam member disposed in said chamber between said stationary cam member and said other end of said housing, said movable cam member being rotatable and axially reciprocable in said chamber; interengageable cam elements on said stationary and movable cam members for moving said movable cam member axially in response to rotation thereof; and means for rotating said movable cam mem- 6. In a rotary hammer, the combination of: a housing providing an axis and providing a generally cylindrical chamber which is open at one end of said housing, the peripheral wall of said chamber being provided with circumferentially spaced spline ways extending parallel to said axis in a direction from said one end of said housing toward the other end thereof and terminating in shoulders disposed in a plane perpendicular to said axis; a stationary cam member disposed in said chamber and having thereon circumferentially spaced splines respectively disposed in said spline ways and seated against said shoulders; means connected to said one end of said housing for maintaining said splines seated against said shoulders, including a head threaded into and closing said open end of said chamber and a spacer clamped between said head and said stationary cam member; a movable cam member disposed in said chamber between said stationary cam member and said other end of said housing, said movable cam member being rotatable and axially reciprocable in said chamber; interengageable cam elements on said stationary and movable cam members for moving said movable carn member axially in response to rotation thereof; and means extending through said head and said stationary cam member and connected to said movable cam member for rotating said movable cam member.

7. In a rotary hammer, the combination of: a housing providing an axis and having therein a chamber provided with end walls; a stationary cam member within said chamber and connected to said housing; a movable cam member within said chamber between said stationary cam member and one of said end walls of said chamber; interengageable cam elements on said stationary and movable cam members for moving said movable cam member axially in response to rotation thereof; means for rotating said movable cam member; and rotatable bearing elements carried by said one end wall of said chamber and engageable with said movable cam member upon axial movement of said movable cam member in a direction away from said stationary cam member.

8. In a rotary hammer, the combination of: a housing; a stationary cam member in and carried by said housing; a movable cam member in said housing adjacent said stationary cam member, said movable cam member being rotatable and reciprocable relative to said stationary cam member; interengageable cam elements on said stationary and movable cam members for moving said movable cam member away from said stationary cam member in response to rotation of said movable cam member; a shaft connected to said movable cam member; bearing means for said shaft carried by said housing and interposed between said shaft and said housing; a drive shaft telescopically related to the shaft first mentioned, one of said shafts having a rectangular, transverse opening therein and the other having longitudinal grooves therein registering with said opening; and a rectangular floating drive pin extending through said opening and into said longitudinal grooves to transmit rotation of said drive shaft to said first-mentioned shaft while permitting reciprocatory motion of the latter relative to the stationary cam member, the dimension of said floating drive pin in the direction of reciprocatory movement of the movable cam member approaching the dimension thereof in a direction transversely of the direction of reciprocatory movement of the movable cam member.

9. In a mechanical hammer, the combination of: stationary and movable cam members disposed in face-toface relation, said movable cam member being rotatable and reciprocable relative to said stationary cam member; and two radially spaced, circumferentially extending rows of circumferentially spaced, rotatable cam elements carried by each of said cam members and projecting therefrom toward the other of said cam members, the cam elements of each of said rows on each of said cam members being engageable with the cam elements of the corresponding row on the other cam member to displace said movable cam member axially away from said stationary cam member in response to rotation of said movable cam member, the cam elements of one of said rows on one of said cam members being circumferentially staggered with respect to the cam elements of the other of said rows on such cam member.

10. In a rotary hammer, the combination of: a housing providing an axis and providing a generally cylindrical chamber which is open at one end of said housing, the peripheral wall of said chamber being provided with circumferentially spaced spline ways extending parallel to said axis in a direction from said one end of said housing toward the other end thereof, said peripheral wall of said chamber providing shoulder means in a plane perpendicular to said axis; a stationary cam member disposed in said chamber and seated on said shoulder means and having thereon circumferentially spaced splines respectively disposed in said spline Ways; means connected to said one end of said housing for maintaining said stationary cam member seated against said shoulder means; a movable cam member disposed in said chamber between said stationary cam member and said other end of said housing, said movable cam member being rotatable and axially reciprocable in said chamber; interengageable cam elements on said stationary and movable cam members for moving said movable cam member axially in response to rotation thereof; and means for rotating said movable cam member.

11. A rotary hammer as defined in claim 5 wherein said movable cam member includes a cam shaft which extends through said other end of said housing and which extends into said head, said rotary hammer including a bearing between said cam shaft and said other end of said housing and a bearing between said cam shaft and said head, said means for rotating said movable cam member including a drive shaft extending through said head and connected to said cam shaft.

References Cited in the file of this patent UNITED STATES PATENTS 1,840,682 Sheldrick et a1. I an. 12, 1932 2,401,794 Pratt June 11, 1946 2,484,471 Shinn Oct. 11, 1949 2,514,759 Hallden July 11, 1950 2,683,362 Bowman July 13, 1954 2,780,106 Lovequist Feb. 5, 1957 

